Ultrasonic agitators are used as cleaning systems in many industrial fields to remove contaminates such as grease, dirt, and/or shavings from a workpiece. Ultrasonic agitators, often referred to as ultrasonic cleaning systems, are used, for example, in the metal working industry to clean elongated metal workpieces, such as wire and stamped parts that are formed from stock material. Typically, ultrasonic cleaning of the workpiece occurs soon after it has been stamped, cut, or otherwise formed. In the metal working industry, the ultrasonic cleaning process is often performed as a precursor to or simultaneous with a pickling process that removes oxides that formed on the surface of the workpiece. In the metal working industry it is important to remove these oxides because their presence adversely affects the ability to bond, coat, or laminate additional layers of material to the surface of the workpiece.
Ultrasonic cleaning is currently performed by placing the workpiece in a cleaning solution which is exposed to low-frequency, 20-40 kHz, vibrations. As a consequence of these vibrations, bubbles, referred to as cavities, form in the solution. These cavities expand until they reach a resonate size at which point they implode. The implosion of the cavities creates very high local pressures and temperatures and generates shock waves within the cleaning solution. The combined effects of the development of these high pressure and temperature zones and the generation of the shock waves scrub off or at least loosen contaminants on the surface of the workpiece.
One such ultrasonic cleaning system is disclosed in German Patent Application No. 27 00 09.6. This document describes an ultrasonic cleaning system wherein a transducer with a cylindrical profile that is between 60 and 300 cm long is used to generate ultrasonic waves in a bath filled with cleaning solution. Great Britain Patent No. 1,591,197 and U.S. Pat. No. 4,401,479 disclose how cylindrical transducers are used to generate sound waves to clean a continuously moving metal wire or strip. Great Britain Patent Application No. 2 030 599 describes an ultrasonic cleaning system in which the workpieces are placed in direct contact with the ultrasonic transducers located within a bath. Once so immersed, contaminates are removed from the workpieces by their direct mechanical vibration and by the cavitation of the surrounding cleaning solution.
While current ultrasonic cleaning systems have proven effective in many environments, they are not without limitations. For example, in the wire industry, multiple parallel wires are often simultaneously produced from the same stock material. A separate ultrasonic transducer system must be provided to generate the requisite sound waves needed to clean each strand of wire. To date, it has proved both difficult and expensive to provide the requisite individual transducers. Furthermore, at the time these wires need to be cleaned, they are travelling at relatively fast speeds, for example, speeds of 50-600 feet per minute or more. To clean these wires ultrasonically, it is usually necessary to immerse them in the vibrating solution for an extended amount of time. Owing to the rate at which these wires move, it has thus become necessary to immerse them in relatively long baths in order to ensure that they are thoroughly cleaned. Still another disadvantage with ultrasonic cleaning systems is that either the transducers themselves, or the transducers in combination with complementary reflectors, completely cover the workpieces they are intended to clean. This makes it very difficult to observe and repair breaks in the workpieces such as wire breaks.
Owing to the difficulties associated with ultrasonic cleaning systems, there have been attempts to find substitute cleaning systems. There have been attempts to use cleaning systems in the form of baths that contain organic solvents at elevated temperatures. Some of the disadvantages of these systems include the necessity of large-sized baths, high operating costs, and the production of waste effluent that must be handled carefully and that is expensive to dispose.